The message edition in Markdown may mess up your nested lists. You can reproduce with this blog content to be posted in a new message in markdown:
* item 1
* subitem 1
* item 2
* subitem 2
PS: the new lines mean that the items content should be wrapped into <p>...</p>. This is IMHO correct Markdown syntax.
The message is displayed OK, but now edit it and you'll get this:
* item 1
* subitem 1
* item 2
* subitem 2
Click "Update". You'll see that your second-level list has been eaten by the first one. Edit to check what's wrong:
* item 1
* subitem 1
* item 2
* subitem 2
Apparently a problems with the HTML to Markdown converter, it doesn't handle lists + empty lines well.